A half cross-sectional view of a conventional electric blower is shown in FIG. 7. In FIG. 7, reference numeral 1 denotes a field core, reference numeral 2 denotes a field winding, reference numeral 3 denotes a spool, reference numeral 4 denotes an armature assembly, reference numeral 5 denotes a motor frame, reference numeral 6 denotes a rotary fan, and reference numeral 7 denotes an air guide. For the electric motor for driving the rotary fan 6 to obtain a suction force, a comutator motor which easily rotates at high speed is used. FIG. 8 shows a plan view only of an electric motor section of a conventional electric blower without a rotary fan and an air guide. In FIG. 8, the field core 1 is fixed in the approximately cylindrical motor frame 5, and such a cross section that facilitates airflow is provided at an outer periphery of the field wiring 2.
The spool 3 is disposed at end surfaces of the field core 1, and a pair of field wirings 2 are arranged around the outer periphery of the spool 3 to form a field assembly. The field assembly is accommodated inside the approximately cylindrical motor frame 5 which is opened at one side, and a space 11 is secured between the field wirings 2 and the motor frame 5. The rotary fan 6 is mounted to an output shaft of the armature assembly disposed inside the field assembly, the air guide 7 is disposed at the outer periphery of the rotary fan 6, and a fan case 10 for covering the rotary fan 6 and the air guide 7 is provided, whereby an airflow passage is formed.
Next, an operation will be explained. When the rotary fan 6 located at the shaft end of the motor is rotated, the air taken in from the rotary fan 6 is guided into the motor via the air guide 7, then passes through the airflow section 11, which is formed between the field core 1 and the motor frame 5, and passes between the field assembly and the armature assembly, and thereafter, the air is discharged outside. The air passing between the field assembly and the armature assembly receives heat transmission from the wirings, and contributes to reduction in wiring temperature. However, most of the air passing through the airflow section 11 formed between the field core 1 and the motor frame 5 is discharged outside the motor without receiving heat transmission from the wirings because there is less airflow towards the vicinity of the wirings.
As the means for suppressing the rise in the wiring temperature of such a motor, there is shown an example of improvement in which a wall is added for closing the airflow section 11 between the end surface of the field core 1 at the side of the fan and the motor frame 5, and thereby the air entering from the fan is passed inside the field core 1 to cool the field wirings 2 and the armature wiring (for example, see Japanese Utility Model Laid-Open No. 59-25957).
There is also shown a configuration in which the inner periphery wall of the spool is inclined inward from the inner diameter of the field core so that it is possible to wind the field wirings 2 inward from the inner diameter of the field core while securing a space between the inner periphery wall of the spool and the armature wiring in order to enhance the effect of cooling the stator and brush for the purpose of enhancement in efficiency and reduction in weight of the motor (for example, see Japanese Patent Application Laid-Open No. 10-42534).
However, in the above-described conventional electric blower, when the air passing inside the motor passes near the wirings, the temperature of the air rises by receiving heat transmission from the wirings, but the air passing through the airflow passage distant from the wirings is discharged outside the motor without receiving heat transmission. The wiring disposed at the side of the fan has a large cooling effect because air flowing from the fan directly blows at the wiring, but the wiring disposed at the opposite side from the fan has a small cooling effect because the temperature of the air passing by has already risen with the heat transmitted from the wiring at the side of the fan. Further, the air flowing near the motor frame distant from the wirings is discharged outside the motor without performing the operation of cooling the wirings, and therefore cooling effect of the wiring is especially low at the opposite side of the fan.
In the configuration in which the air entering from the fan is passed to an inside of the field core by adding the wall for closing the airflow sectional area between the field core end surface at the side of the fan and the motor frame so that the field wirings and the armature wiring are cooled, thereby to improve the wiring cooling effect of air which passes inside the motor, an airflow does not exist in the section formed between the field core and the motor frame. Therefore, there exists a problem that the cooling effect of the field wiring at the opposite side of the fan is weak, and the temperature difference between the field wirings at the fan side and the opposite side of the fan is large. Further, there exists another problem that the pressure loss of the airflow increases, and the blower efficiency reduces because the sectional area through which the air discharged from the fan can enter the motor becomes small.
With the configuration in which the inner periphery wall of the spool is inclined inward to shorten the coil end between the slots of the field wiring, the effect of the guide for guiding wind to the commutator disposed inside the field wirings can be obtained. However, since the inner periphery wall of the spool exists in each space formed adjacent the field wirings, the wind which passes between the field assembly and the armature assembly is discharged without receiving transmission of the heat from the field wirings. In addition, with this configuration, the field wirings hardly expose outside from the field core so that air flowing outside the field hardly hits the filed wirings either. Thus, cooling capability of the field wirings is reduced, and rise in the temperature of the field wirings is increased.
Because of these problems, the rise in temperature of the wirings becomes high when the power consumption is made large, and therefore the improvement means for suppressing the wiring resistance by increasing the physical constitution of the motor is required. For this purpose, improvement in the cooling performance which makes it possible to reduce the size and weight of the motor is strongly demanded.
In order not to reduce the efficiency of the electric blower, such an improvement is demanded to enhance the wiring cooling performance while suppressing the increase in loss of inflow into the motor as a blower.